Heat only comes through the vent

My 2000 century buick recently only blew heat on highest setting with fan. Now it will only allow heat to flow not blow, but flow through the vents. Is my fan broken or is it a fuse? or what? can anyone help me please! thank you!

It sounds like your blower resistor pack has blown. A good independent mechanic will have it going in no time.

Missleman NAILED IT… It is the resistor pack that controls your fan motor. This pack is what gives you different fan “speeds” The lower speeds burn out first as these are the most heavily “resisted” settings…the last fan speed…which is FULL Speed is NOT resisted…it is a direct connect to the 12V battery…and thus…goes as fast as possible.

You can either grab one of these packs from the junkyard or buy new. The pack is USUALLY located behind your Glove box…You drop your glove box Door down and out of the way…and the resistor pack is USUALLY directly behind the glove box door. This is an ez fix to a simple issue actually


If there’s air only coming out the vents, and you’re unable to switch to defrost or floor mode the problem might be with the HVAC control module.


The HVAC control module is what controls vent system modes and also the blower speeds.


Resister pack.
The blowers use 12VDC motors. DC motors can be speed-controlled by simply varying the applied voltage. It’ll go slower on 9VDC than on 12VDC. To establish the different voltage levels, manufacturers commonly simply put a stepped-resister network in series with the motor voltage. Put the fan switch on HI and the full 12VDC is applied, not resisters are used.
Put the switch on 3 and a resister is introduced to the circuit to “drop” the voltage to 9VDC.
Put the switch on 2 and another resister is added to the circuit to “drop” a bit more voltage and the motor now sees 6VDC.

As these resisters burn out, the lower speeds disappear, because the burned out resisters no longer conduct. The last leg of the circuit to go is the HI speed, because that’s without the resisters.

The reason the resisters burn out, by the way, is because they convert the voltage they “drop” into heat.


Judging from the title of the posting, can I assume that air ONLY comes from the defroster vents?

And nowhere else?